bug#74230: 30.0.92; eshell-emit-prompt clobbers text properties

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 7 Nov 2024 10:16:16 -0800
> Cc: eliz@gnu.org
> From: Jim Porter <jporterbugs@gmail.com>
> 
> On 11/6/2024 10:21 AM, Ashton Wiersdorf wrote:
> > In Emacs 29.4, the function did *not* overwrite the text properties of
> > the prompt `rear-nonsticky (read-only)`. The new version overwrites the
> > rear-nonsticky property so that it is only `(field)`.
> 
> Thanks for noticing this.
> 
> > If I set `eshell-highlight-prompt' to `t', then I get the read-only
> > behavior that I want, but now I cannot get the pleasant component
> > highlighting that `fancy-shell' is meant to provide.
> 
> If you set the 'face' attribute instead of the 'font-lock-face' 
> attribute, you should get the highlighting you want (that's what I do) 
> while 'eshell-highlight-prompt' is non-nil.
> 
> Here's a patch to fix this though so that we're more careful about not 
> clobbering stickiness properties. Eli, what do you think about this 
> patch? It fixes a regression from Emacs 29, but the diff is fairly large 
> for so late in the Emacs 30 cycle. Unfortunately, I can't think of a 
> better solution that doesn't just shuffle the bug around to a different 
> spot. On the plus side, this code already has regression tests, and it 
> was easy to add a new one for this case.
> 
> Personally, I'd be ok with having this be a known bug (there's a 
> workaround for Emacs 30) and fixing it on master. But if you think this 
> change is ok for the release branch, I'd also be ok with installing 
> there; then people don't need to deal with the workaround.

I agree, let's fix this on master.

Thanks.